Salivary glands are innovated by the autonomic nerve. The stimulations of muscarinic and a- and b- adrenergic receptors in the tissues activate the salivary secretion. Aquaporin-5 which was cloned from submandibular glands was shown to be localized topographically in the apical plasma membrane (APM) of duct cells in rat parotid glands. In this investigation, to evaluate the role of aquaporin-5 in salivary secretion induced by nervous stimulation, the alteration of the distribution of aquaporin-5 in rat parotid tissues induced by acetylcholine or epinephrine was studied by immunoblot analysis. The treatment of the tissues with acetylcholine or epinephrine within 1 min induced the increase in the amount of aquaporin-5 in APM, but that for more than 10 min resulted in the decrease of the amount of aquaporin-5 in APM.Acetylcholine-induced increase in the amount of aquaporin-5 in APM was inhibited by atropine, p-F-HHSiD and TMB-8, but not by methoctramine, GF-109203X or H-7. A-23187 alone
… Morestimulated the increase in the amount of aquaporin-5 in APM.While, epinephrine-induced increase in the amount of aquaporin-5 in APM was mimicked by phenylephrine, but not by clonidine, dobutamine, or salbutamol. It was inhibited by phentolamine, but not by propranolol. Furthermore, epinephrinethe-induced increase of aquaporin-5 was inhibited by cytochalasin-D and tubulozole-C.These results indicated that acetylcholine and epinephrine acted on M3-muscarinic and al-adrenergic receptors, respectively and induced the increase in the amount of aquaporin-5 in APM, and that [Ca2+]i elevation by acetylcholine or epinephrine may play a key role in this increase. In addition the involvement of the cytoskeleton was shown in these induction. The increase of the amount of aquaporin-5 in APM by acetylcholine was 3-fold in the tissues of young adult rats, but 2-fold in those of senescent rats. The difference between the amounts of aquaporin-5 in APM in these rats may depend on that between the [Ca2+]i elevated by acetylcholine.2.耳下腺切片をエピネフリン(Epi)との反応によって、管腔膜のAQP5は約2倍の増量が認められ、これは、α1-アドレナリン受容体を介していた。3.8週齢、104週齢ラット耳下腺切片を用いてM3-ムスカリン作動薬又はα1-アドレナリン作動薬と反応させ管腔膜AQP5量を測定すると、M3-ムスカリン作動薬では8週齢ラットで3倍、104週齢ラットで2倍の管腔膜AQP5の増量が認められ、α1-アドレナリン作動薬では8週齢,104週齢ラットとも2倍の管腔膜AQP5の増量が認められた。4.IP3受容体とリアノジン受容体の加齢変化をウェスタンブロッティングで測定したところ、両受容体に加齢変化は認められなかった。5.[Ca^<2+>]iの加齢変化を、8週齢、104週齢ラット耳下腺遊離細胞にFura-2を取り込ませて、蛍光光度計を用いて測定したところ、老性低下が認められた。 3〜5のことから、M3-ムスカリン作動薬による耳下腺管腔膜におけるAQP5増量の老性低下は、[Ca^<2+>]iのM3-ムスカリン作動薬による上昇の老性低下に起因するものと推察された。 また、平成10、11、12年度の成果をまとめて総説をJapanese Journal Pharmacology,83,95-101,2000に記した。 Less